Background Gamma Activity in the Electroencephalogram as a Measure of the Level of Sustained (tonic) Attention during Execution of the “Active Oddball” Paradigm in rabbits
Tonic brain activity has significant influences on the nature of a subject’s responses to target sensory stimuli. We report here studies of the dynamics of the background activity in the gamma-rhythm range of the EEG in rabbits during execution of an “active oddball” paradigm modified for animals – a task widely used for studies of attention. Increased levels of power and coherence in background gamma activity were found to reflect expectation of a target stimulus, correct responses to stimuli being executed at a particular level of background gamma activity which probably corresponds to the optimum level of sustained (tonic) attention. Decreases in the level of gamma activity led to missed responses to the target stimulus, while excess levels lead to erroneous responses to non-target signals (false anxiety). These dynamics of background gamma activity are interpreted as resulting from oscillations in the level of tonic cholinergic activation of right cerebral cortex.